It is a 55 gallon tank, my son took his fish out last week because of Ick and the only things left in it are corals, a starfish, and a crab. The corals are all doing better than ever before but his ammonia levels are up.

Do you have live rock in the tank?
How much?
A skimmer?
How many fish were in the tank?
What kind and how big?
Any new additions before the Ammonia went up? Any deaths?
What test kit are you using? Is it within expiration?